Assessing Your Exchange Server 2003 Design Requirements

Topic Last Modified: 2005-05-13

Business, administrative, user, and security requirements directly affect the design of your Exchange Server 2003 messaging system. Because companies use various methodologies to gather and document requirements unique to their situations, this section does not provide an exhaustive list of all possible requirements. Instead, it focuses on some general types of requirements and the issues associated with each that can influence your planning.

Some of the business requirements that you need to identify before you begin planning an Exchange messaging system include the following:

Service Level Agreements (SLAs)

Network and hardware cost constraints

Software cost constraints

Business requirements, particularly cost constraints, determine the extent to which you must work within the existing infrastructure or whether it is feasible to upgrade the network infrastructure, hardware, and software.

Service Level Agreement (SLA) requirements determine how things such as storage, clustering, and backup and recovery factor into your system. When assessing SLAs, be sure to determine your company's expectations regarding availability and recoverability, including message delivery time, percentage of server uptime, amount of storage per user, and amount of time to recover an Exchange database. Identify the hours of regular operation and the expectations around planned downtime. In addition, identify the company's estimated cost of unplanned downtime so that you can design the proper amount of fault tolerance into your messaging system.

New features in Exchange Server 2003 and Windows Server 2003 may affect the way you design your system to meet SLAs. In particular, the new Volume Shadow Copy service may challenge the limits that your SLAs previously imposed. Because backups can take a long time to complete, you previously may have had to limit the number of users you hosted on each mailbox store to meet SLA limitations for uptime. With Volume Shadow Copy service, however, the backup is performed from the shadow copy, so there is no affect on the database that the applications are using. Volume Shadow Copy service allows you to back up Exchange data (or any application data) quickly and with minimal impact to your e-mail clients. This helps you support larger databases and more users per server. When used in conjunction with software and hardware that supports Windows Server 2003 Volume Shadow Copy service, you can quickly back up or restore Exchange databases of any size, from 100 GB to several terabytes. You can also set up clusters that exist in different physical locations. All of these features provide improved service levels than may have been previously possible.

Financial constraints surrounding upgrades to the existing network and hardware directly affect the design of your Exchange messaging system. Depending on the integrity of your existing network, certain upgrades may be necessary to meet business and user requirements. In cases where upgrade possibilities are limited, you may or may not be able to take advantage of certain messaging features, such as RPC over HTTP in Exchange 2003. This feature can help you provide a better messaging experience over existing low-speed, unreliable network connections.

If it is part of your business strategy to reduce total cost of ownership by consolidating or centralizing server hardware, certain features in Exchange 2003, Windows Server 2003, and Outlook 2003 can help facilitate this strategy. For example, Exchange 2003 is less subject to memory fragmentation, which means that Exchange 2003 servers with fast processors can handle more users per server before reaching a memory fragmentation limit. This is also the case with Windows Server 2003, which manages memory better so you can host more users on a server before you encounter memory fragmentation issues. Better memory management does not necessarily mean that you will see significant gains in CPU performance or scalability, but usually you can host more users on a server.

Your company's administrative requirements have a significant impact on system design, especially if you want to reduce administrative costs by moving toward a more centralized model.

Businesses usually implement administrative models that generally fall into two categories:

Centralized management A single group maintains complete control of the Exchange system. With this model, you implement a small number of administrative groups, whether you have a single data center or a large number of branch offices. A single information technology group performs all administrative tasks. This model is typical in small- or medium-sized companies, but can also be used in larger companies that have high bandwidth connectivity between all regional offices.

Distributed management Complete control over management of the Exchange system is distributed to company regions or divisions. The company might create at least one administrative group for each region or division, with each administrative group containing routing groups, policies, servers, public folder directory hierarchies, and other objects specific to each division. A central information technology group may be responsible for managing standards and guidelines, but not for daily system administration. Usually, each region or division controls its own assets and performs its own system administration.

Note:

In Exchange 5.5, a site defines both administrative and routing boundaries. In Exchange 2000, the site concept is split into routing groups and administrative groups for greater flexibility. In Exchange 2000 and Exchange 2003, a routing group refers to a collection of full-time, reliable servers in which messages are routed directly from server to server. An administrative group refers to a collection of users with administrative authority and is not confined by routing group boundaries.

Understanding your company's administrative requirements helps you determine whether to implement a centralized model, a distributed model, or a combination of the two. For more information about the interdependencies between Exchange administration and the Active Directory® directory service administration, see "Understanding Your Current Network Environment".

Some of the user requirements that determine how you plan your Exchange messaging system include the following:

Remote access In companies whose offices are geographically dispersed and connected by slow- and low-bandwidth network connections, users may require a better offline experience. By assessing this requirement along with your business requirements and constraints, you can determine whether you can take advantage of features such as Cached Exchange Mode in Outlook 2003 to provide a better offline experience.

Web access Users may require the ability to access their Exchange information from the Internet. Several changes to Microsoft Office Outlook Web Access 2003 in the areas of user interface and performance improve the experience for users in remote offices. However, investments in operating system upgrades may be required; for example, the performance gains that result from new compression technology rely on using Windows Server 2003 as the operating system.

Your security requirements may affect your Active Directory design. For example, your company may require strict security boundaries between directories for separate business units, which means that you may need to establish multiple forests. For more information about establishing multiple forests, see "Planning to Deploy Exchange in a Multiple Forest Environment."